Hiwula’s composed finish was his first goal for Rovers and also his first of 2021.
The 27-year-old last found the net in December 2020 with a brace for Portsmouth at Cheltenham in the Papa John’s Trophy.
Hiwula missed the start of the season with an ankle injury and, as he continues to build up his match sharpness, will be buoyed by getting off the mark.
But he also wasted another great second half chance at Home Park when he shot wide with the goal at his mercy and later saw another attempt cleared off the line by backtracking Plymouth defender James Wilson.
And Wellens had a clear message for Hiwula ahead of tonight’s game at Ipswich Town.
"He should’ve had his first hat trick,” said Wellens, reflecting on Saturday's game.
“It was a nice finish. And, okay, he wants the second one to be a nice finish, and then the next one a nice finish.
“Hit the target. Pick where you’re going to put it and put it in with power and don’t give the defenders opportunities to get back.
“Even though I’m really pleased for him I know that he can get 15 goals in this league.
“Be more ruthless, because if he’s more ruthless when he gets into those areas his goal tally will increase.”
Hiwula’s best goal return is the 13 he scored for Coventry in League One in 2018/19.